6 INTRODUCTION TO COLUMN BUCKLING

INTRODUCTION TO COLUMN BUCKLING . 6 INTRODUCTION TO COLUMN BUCKLING . INTRODUCTION AND BASIC CONCEPTS. There are many types of compression members, the COLUMN being the best known. Top chords of trusses, bracing members and compression flanges of built up beams and rolled beams are all examples of compression elements. Columns are usually thought of as straight vertical members whose lengths are considerably greater than their cross- sectional dimensions. An initially straight strut or COLUMN , compressed by gradually increasing equal and opposite axial forces at the ends is considered first. Columns and struts are termed long or short depending on their proneness to BUCKLING . If the strut is short , the applied forces will cause a compressive strain , which results in the shortening of the strut in the direction of the applied forces. Under incremental loading, this shortening continues until the COLUMN "squashes". However, if the strut is long , similar axial shortening is observed only at the initial stages of incremental loading.

Elastic buckling stress (σcr) defined by (π 2E/ λ2) σcr (Mpa) λ = λ/r Fig. 4 Euler buckling relation between σ cr and λ 3.0 STRENGTH CURVE FOR AN IDEAL STRUT We will assume that the stress-strain relationship of the material of the column is defined by Fig. 5. A strut under compression can therefore resist only a maximum force given by fy.

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